(1) Field of the Invention
The invention relates to MEMS G-switches, and more particularly, to a MEMS structure having a larger capacitance when the MEMS G-switch is turned on and a smaller capacitance when the MEMS G-switch is turned off.
(2) Description of the Related Art
Micro-electro-mechanical systems (MEMS) are devices which may be fabricated using semiconductor thin film technology in order to reduce the characteristic dimensions and, thus, the cost of the devices. MEMS have been spotlighted recently because of their increasing application to a wider range of fields. Many micro-mechanical sensing devices are now well known. Such devices include sensors of all types. These devices are termed “micro-mechanical” because of their small dimensions on the order of a few centimeters square or smaller. The small size is generally achieved by employing photolithographic technology similar to that employed in the fabrication of integrated circuit (IC) dies. With this technology, the devices are as small as microelectronic circuits, and many such devices are often fabricated in a batch on a single substrate, thereby dividing the cost of processing among many individual devices. The resulting low unit cost increases the application for such devices.
The MEMS G-switch is one of the physiological sensing or intelligent monitoring devices providing miniature, lightweight and ultra-low power as required for health monitoring applications or consumer electronics, for example.
U.S. Pat. No. 6,765,160 (Robinson) discloses a G-switch that is closed when a proof mass makes contact with a bottom ring electrode. U.S. Pat. No. 7,316,186 (Robinson et al) describes a submunition having a MEMS G-switch that closes upon impact. U.S. Pat. No. 6,035,694 (Dupuie et al) describes calculating stray capacitance by sensing the position of a MEMS proof mass. U.S. Pat. No. 6,550,330 (Waters et al) and U.S. Patent Applications 2006/0161211 (Thompson et al) and 2003/0140699 (Pike et al) disclose various MEMS accelerometers.